Aristotle’s students gathered descriptions of 158 Greek city-states, which Aristotleused to formulate his famous sixfold typology of political systems. He distinguished political systems by the number of persons ruling (one, few, or many) and by whether the form was legitimate (rulers governing in the interests of all) or corrupt (rulers governing in their own interests). Legitimate systems included monarchy (rule by one), aristocracy (rule by the few), and polity (rule by the many), while corresponding corrupt forms were tyranny, oligarchy, and democracy. Aristotle considereddemocracy to be the worst form of government, though in his classification it meant mob rule. The best form of government, a polity, was, in contemporary terms, akin to an efficient, stable democracy. Aristotle presciently noted that a polity functions best if the middle class is large, a point confirmed by modern empirical findings. Aristotle’s classification endured for centuries and is still helpful in understanding political systems.